| 摘要 |
System for transmitting digital-signals over an electrical power distribution circuit by the same modulating at least two different carrier signals. The carrier signals are derived by frequency division from a common master oscillator, and are thus phase-coherent. The system includes a receiver, comprising a respective input circuit for each modulated carrier. A plurality of oscillator signals of different frequencies, derived from a variable frequency oscillator, are used to beat the received carrier signals to respective signals at a common frequency, which signals are summed. This signal is applied to one input of a phase detector, whose other input is connected to receive another common frequency signal from the variable frequency oscillator. The output signal from the phase detector is applied to the variable frequency oscillator to lock its frequency to those of all the carriers and therefore to that of the master oscillator in the transmitter. |
